Add deprecation warnings

Author: samudary

README.md

@@ -77,6 +77,8 @@ The following methods are currently available on the client instance. You can fi
 | List all forms                       | `client.listForms(callback)`                                                 |
 | Fetch a form                         | `client.fetchForm(formId, callback)`                                         |
 
+**Note:** The beta purchases endpoint has been deprecated and its methods have been removed from the package except `createPurchase`, which now sends requests to the Order creation endpoint [here](https://developer.drip.com/#orders).
+
 ### Orders
 | Action                               | Method                                                                       |
 |--------------------------------------|------------------------------------------------------------------------------|

lib/purchases.js

@@ -1,6 +1,10 @@
 module.exports = {
   /**
    * Record purchases for a subscriber
+   * 
+   * @deprecated Deprecated since version 2.0.0. Will be deleted in version 3.0.0.
+   * The beta Purchase endpoint has been deprecated and this method now sends requests
+   * to the Order creation endpoint. Please use `createUpdateOrder` instead
    *
    * @param {string} idOrEmail - The subscriber's email or id
    * @param {object} payload - An object with purchase details